The use of sprinklers is a common method of irrigating areas of grass, trees, flowers, crops, and other types of vegetation. In a typical irrigation system, many different types of sprinklers may be used to distribute water over a desired area. One type of irrigation sprinkler that is commonly used is a spray head sprinkler having a nozzle that produces a fan-shaped spray projected outwardly in an arcuate pattern about the sprinkler. Typically, such spray heads are mounted on either stationary risers or on pop-up risers that are movably mounted in a housing buried in the ground. In case of a pop-up riser, the riser is retracted into the housing when the sprinkler is not in operation and extends out of the housing and above the ground when the sprinkler is in operation. There are several concerns, however, that arise when using such variable arc spray nozzles: (1) insufficient adjustability of the arcuate span of the water distribution; (2) insufficient water distribution to terrain relatively close to the sprinkler; (3) lack of a uniform water precipitation rate between arcs of different spans; and (4) lack of uniform water distribution at the edges of the distribution pattern.
First, in many instances, it is desirable to control the arcuate area over which the sprinkler distributes water. In this regard, it is often desirable to use a spray nozzle that distributes water through a variable pattern in virtually infinite arcuate settings between a full circle pattern and a very small arcuate pattern of about 5° or less.
Second, it is desirable to have a portion of the spray distributed close in to the sprinkler to avoid producing a donut-shaped watering pattern about the sprinkler. Many commercially available variable arc spray nozzles tend to distribute water in a donut-shaped pattern with little water being distributed in the region close to the sprinkler. Thus, regions that are further from the sprinkler generally receive more water than regions that are closer to the sprinkler. Accordingly, there is a need for a variable arc nozzle that provides a water distribution pattern that includes appropriate watering near the sprinkler.
Third, variable arc nozzles often generate different precipitation rates, depending on the size of the arcuate span of water distribution selected by the user. Generally, smaller arc settings tend to result in higher precipitation rates because a given amount of water is distributed over a smaller area. For example, when the size of the arc is reduced (such as from full circle to half circle), if the flow rate is not also reduced, the resulting precipitation rate will be relatively high for the reduced area of coverage. In most instances, it is highly desirable that each sprinkler in the system provide a uniform amount of water to the selected watering area so that all vegetation receives the same amount of water over a given time regardless of the arcuate span of the water distribution. Thus, there is a need for a variable arc nozzle that proportionally adjusts the flow rate through the nozzle as the arcuate span of the water distribution is adjusted by the user.
Typically, the water precipitation rate of conventional spray head sprinklers is generally not homogenous along the radius of distribution. The water precipitation rate depends on the square of the distance from the sprinkler. Accordingly, in many instances, the flow rates of nozzles are specifically set by the manufacturer to different amounts depending on the radius of coverage of the nozzle. The flow rates of nozzles designed for closer ranges of coverage, such as four, six, or eight feet, are therefore less than that for nozzles designed for more distant ranges of coverage, such as ten, twelve, or fifteen feet.
One method of decreasing flow rate is by the use of arcuate water outlet spray slots that are relatively narrow, e.g., on the order of 0.02 inches. The use of these relatively narrow slots is especially common for fan spray nozzles intended to provide a relatively close range of coverage, such as four, six, or eight feet. These narrow slots, however, are easily clogged by dirt or other debris. Thus, there is a need for variable arc nozzles that proportionally adjust the flow rate through the nozzle to avoid using narrow arcuate outlet slots that can become clogged.
Fourth, there is a need to improve the water definition and evenness at the edges of the water distribution arc. There are often irregularities and gaps at the edges of the arc. For example, while water in the central part of an arc distribution pattern is generally thrown a uniform distance from the nozzle, the water at the edges of the arc is not thrown as far. Also, even for terrain along the edges relatively close to the nozzle, there is uneven water distribution. Where multiple sprinklers are used to cover a given terrain, this unevenness at the edges results in gaps of coverage and non-uniform coverage, especially at the transition areas from one sprinkler's coverage to another and at areas close to the individual sprinklers.
The irregularities and gaps at the edges result from components of the variable arc nozzle known as edge “fins,” which are used to define the size of the water distribution arc. The gaps and irregularities at the edges of the water distribution arc generally arise from three factors associated with these edge fins. First, the fins generate frictional drag against water distributed at the edges of the pattern that is not present at the center of the pattern where there are no fins. This drag, in turn, reduces the throw distance of water at the edges of the arc distribution pattern. Second, there is a significant tangential component of water flow at the edge fins. Some of the tangential flow results from leakage between mating components of the nozzle, causing deflection of a portion of the outwardly projected flow and resulting in gaps and uneven water distribution. Third, conventional edge fins do not sufficiently channel the outwardly projected flow along the edges of the arc, again resulting in a tangential component of flow and uneven water distribution.
Accordingly, it is desirable to have a variable arc nozzle that: (1) adjusts to about any desired arcuate span of water distribution; (2) provides increased water distribution to terrain near the sprinkler; (3) provides a relatively constant water precipitation rate regardless of the size of the arcuate span of water distribution selected by the user; and (4) provides a water distribution arc with fairly even water distribution at the edges of the arc. Depending on the specific needs of the user, it may be desirable to incorporate one or more of the above features into a given variable arc nozzle. The present invention fulfills these needs and provides further related advantages.